Marginal analysis of the cost of driving to Pittsburgh

Consider the following costs of owning and operating a car. A $25,000 Ford Taurus financed over 60 months at 7 percent interest means a monthly payment of $495.03. Insurance costs $100 a month regardless of how much you drive. The car gets 20 miles per gallon and uses unleaded regular gasoline that costs $3.50 per gallon. Finally, suppose that wear and tear on the car costs about 15 cents a mile. Which costs are fixed, and which are variable? What is the marginal cost of a mile driven? In deciding whether to drive from New York to Pittsburgh (about 1,000 miles round trip) to visit a friend, which costs would you consider? Why?